Anatomy 2: Ear Flashcards
Give 3 features of the Pterion
1) H-shaped suture
2) Consists of the frontal, parietal, temporal and sphenoid bone
3) THINNEST part of the skull
What are the 2 parts of the temporal bone?
The squamous part
The petrous part
What 2 bones make up the middle cranial fossa?
Sphenoid and temporal bone
What part is the external ear?
What is the job in the external ear?
Auricle –tympanic membrane
Collects and conveys sounds waves to tympanic membrane
What part is the middle ear?
What happens here?
Tympanic membrane – Oval window
Amplifies and conducts sound waves into internal ear
What part is the internal ear?
What happens here?
Oval window -- internal acoustic meatus Converts special sensory info: 1) Into fluid waves 2) Then action potentials 3)Conducts APs to brain
What is the general sensory nerve supply to the outer ear and describe its approx. whereabouts
C2,3 spinal nerve on the outside HELIX part
CNV3 + CNX in inner part towards tympanic membrane with CNVII mixed in !!
What kind of cartilage is within the external ear?
Elastic
Describe the sensory nerve supply in middle ear
Tympanic membrane is mostly CNV3
CNIX: Internal surface + Middle ear cavity + Eustachian tube + Nasopharynx + Oropharynx + Tonsils
What are the 3 bones (in order of external -internal) within the middle ear cavity
Malleus // Incus // Stapes
What do the 3 bones of the middle cavity join by?
Synovial joints
What does the Eustachian tube connect?
The middle ear cavity to the nasopharynx
How could earache mean you have tonsillitis?
The Eustachian tube & the nasopharynx have a shared nerve supply - CNIX
How is the facial nerve involved within the middle ear cavity?
1) The chorda tympani (branch from CNVII) is present
2) CNVII innervates the right stapedius (reduces stapes movement so protects from very loud sounds)
What does the chorda tympani do?
Parasympathetic supply to submandibular and sublingual glands
What supplies the muscles of facial expression?
CNVII
Describe the nerve supply to the internal ear
CNVIII - divided into 2 parts
The cochlear nerve (hearing)
The vestibular nerve (balance)
What is the shell-like structure in the internal ear called? Where is it located?
The otic capsule
Located in the temporal bone
Swirly bit = ‘Cochlea’
What is contained within the otic capsule?
Bony labyrinth which is fluid filled ('perilymph')
Within the perilymph there is...
1) Membranous labyrinth
2) Communicating sacs + ducts
3) Ducts contain Endolymph fluidDescribe the 7 steps of sound transmission
1) Sound waves make tympanic membrane vibrate
2) Vibrations transmitted through ossicles
3) Base of stapes vibrates in oval window
4) Vibration of stapes creates pressure waves in perilymph
5) Hair cells in the cochlea are moved, neurotransmitter is released, APs stimulated and conveyed to brain by cochlear nerve
6) Pressure waves descend and become vibrations again
7) Pressure waves are dampened at the round window
